MedicalResearch.com Interview with: Joshua W. Miller, PhD Professor and Chair Dept. of Nutritional Sciences Rutgers The State University of New Jersey New Brunswick, NJ 08901  Medical Research: What is the background for this study? What are the main findings? Response: In recent years, there has been a growing scientific literature on the associations between low vitamin D status in older adults and risk of Alzheimer's disease/dementia, cognitive impairment and decline, and brain atrophy.  The vast majority of these studies have been conducted in predominantly white populations.  The relatively unique aspect of our study was that over half of the cohort consisted of African Americans and Hispanics.  What we found in our cohort (mean age ~75y, n=382 at baseline) was that participants with vitamin D deficiency (serum 25-hydroxyvitamin D <12 ng/ml) or vitamin D insufficiency (serum 25-hydroxyvitamin D between 12 ng/ml and <20 ng/ml) on average experienced faster rates of cognitive decline in episodic memory and executive function than participants with adequate vitamin D status.  Importantly, the association between vitamin D status and the rate of decline in cognitive function was independent of race/ethnicity.  However, the prevalence of low vitamin D status in the study participants was significantly higher in the African American and Hispanic participants compared with the White participants.  This is most likely due to the fact that darker skin pigmentation reduces the ability of sunlight to induce vitamin D synthesis in the skin.  It may also reflect differences in dietary intake of vitamin D and supplement use between the different race/ethnicity groups, though we did not assess this in our study.  Thus, though the rate of cognitive decline in African Americans and Hispanics does not seem to be more or less affected by low vitamin D status than in Whites, because African Americans and Hispanics have a higher prevalence of low vitamin D status, as subpopulations they may be more prone to rapid cognitive decline in old age.  Further studies addressing this possibility are needed. (more…)